In recent years, techniques of using a tape automated bonding process (generally referred to as the TAB process) to package integrated circuit chips have been developed. The TAB process replaces other lead-frame wire bonding methods that are currently used in packaging integrated circuit chips. In one form of the TAB process, an integrated circuit chip is directly bonded to a foil-type lead frame that is usually rolled to about 0.08 mm in thickness. The inner ends of the leads that were etched into the foil tape are bonded to the solder bumps on the integrated circuit chips by a thermal compression method.
The integrated circuit chip is then encapsulated in plastic in an injection molding process leaving the outer ends of the leads exposed to the outside of the integrated circuit. The encapsulated integrated circuit and the exposed leads can then be excised out of the tape for connection to a circuit board. We shall use the term an integrated circuit module to describe an encapsulated TAB integrated circuit and its exposed leads.
In an encapsulated TAB integrated circuit module, the integrated circuit chip itself is well protected by the encapsulating plastic. However, the leads which are formed of tin plated copper foil are exposed for necessary connection to a circuit board. The dimensions of these leads which are approximately 0.3 mm wide, 0.08 mm thick, and 5 mm long make them very fragile and susceptible to damages during manufacturing and assembly. The fact that these leads are closely spaced together and in close proximity to the encapsulated chip make them almost impossible to repair once they are damaged.
It is therefore an object of the present invention to provide an integrated circuit package for surface mounting wherein the package leads to the integrated circuit chip are protected from deformation and damage during the manufacturing and assembly process.
It is another object of the present invention to provide an integrated circuit package for surface mounting wherein the leads to the integrated circuit chip can be formed into desirable shapes and nested in sockets to be connected to socket pins upstanding on a circuit board.